Tunnel Jacking Research Articles

Deformations of Subway Tunnels Induced by the Overcrossing Jacked Box Tunnels

The rectangular utility tunnels have been increasingly built in urban areas in recent decades. In this paper, a case of jacked box tunnels built closely over-crossing the existing subway tunnels in Suzhou, China, is presented. The tunneling-induced deformation of the subway tunnels is measured and analyzed. The measurement indicates that the subway tunnels are uplifted and subjected to the overcrossing box tunneling. As compared, the longitudinal deformation of the range that locates under the box tunnels is more significant than that outside the range. The tunneling-induced deformation of the left subway tunnel is relatively higher than that of the right one. The numerical simulation is performed for validation. The numerical result is agreed with the in-situ measurements. Moreover, the simulation reveals that the presence of friction in jacked tunnels causes the extra uplift deformation of subway tunnels. The higher the friction, the is the deformation. It is affirmed that using the effective lubrication not only facilitates the tunnel jacking but also inabilities the tunneling-induced deformation of underlying tunnels

EFFECT OF NOSE BLADE ANGLE ON FACE STABILITY OF JACKED BOX TUNNELLING

A typical jacked box tunnel usually consists of a precast concrete box tunnel and a steel nose blade installed in the box front. Two of many design factors for this tunnel type are the face stability and the face resistance; an increase in face stability is typically accompanied by an unintended consequence of an increase in face resistance. A series of numerical analyses was performed to explore the interaction between the face stability and the face resistance. Three design parameters were considered, namely amount of unexcavated soil inside box tunnel, nose blade angle and soil depth. Plane strain finite element models were used to simulate the tunnel jacking process; the software used was Plaxis 2D. The face stability represented by safety factor is affected mainly in a decreasing order by the amount of unexcavated soil inside box tunnel and the nose blade angle. However, if a minimum jacking force is required, an optimal combination of the two design parameters should be adopted.

An optimization model for urban sewer system hydraulic design

A gravity sewer system is a multi‐stage multi‐option system composed of a series of pipes and manholes. For each sewer pipe stage, there are several different commercial pipe sizes available as options. A comparison of optimum design alternatives thus becomes very complex, due to the number of combinations of commercial pipe sizes and slopes that must be evaluated in terms of hydraulics. Therefore, a Sewer System Optimization Model (SSOM) for hydraulic designs is developed. The model uses 0–1 mixed integer programming (MIP) and an efficient screening algorithm, the bounded implicit enumeration (BIE) algorithm. The first consideration is to provide a set of design variables for urban sewer system design problems corresponding to the various construction modes. A 73‐manhole open‐cut method model is tested. The results indicate that this approach is more cost‐effective than other previously developed optimization models and techniques. As well, a practical sewer system construction case in Taipei is selected, to compare with the traditional design approach. The obtained design results show that the SSOM program, based on tunnel jacking construction, can be used for this practical design. It has the effect of saving 12% on piping and 40% on pumping heads during construction.

Airway disease in highway and tunnel construction workers exposed to silica

Construction workers employed in a unique type of tunnel construction known as tunnel jacking were exposed over an 18-month period to respirable crystalline silica at concentrations that exceeded the OSHA permissible exposure limit. The present study examines workplace exposures and occurrence of airway disease in these workers. Medical and occupational histories and chest radiographs were obtained on 343 active construction workers who had worked on the site during the period in question. Chest radiographs were interpreted according to the ILO-1980 system of classification. Standardized questions were used to develop an algorithm to define symptoms consistent with asthma (SCA) and to determine these respiratory outcomes: chronic bronchitis, shortness of breath (SOB), and physician-diagnosed asthma (current vs. not current). Relationships with each of three work activities were examined: slurry wall breakthrough (SWB), chipping caisson overpour, and tunneling/mining. Participants included laborers, carpenters, tunnel workers, ironworkers, operating engineers, and electricians. No cases of silicosis were found on chest X-ray. Overall prevalence of chronic bronchitis, SCA, SOB, and physician-diagnosed asthma was 10.7%, 25%, 29%, and 6.6%, respectively. Odds ratios (OR) for carpenters compared to laborers were significantly elevated for chronic bronchitis, SCA, and SOB. SWB was associated with chronic bronchitis and SCA (OR 4.93, 95% CI = 1.01, 24.17; OR 3.32, 95% CI = 1.25, 8.84, respectively). The interaction between SWB, SCA, and trade was significant for carpenters (OR 6.87, 95% CI = 1.66, 28.39). Inverse trends were observed for months on the site and chronic bronchitis, SCA, and SOB (P = 0.0374, 0.0006, and 0.0307, respectively). Tunnel construction workers exposed to respirable crystalline silica and cement dust are at increased risk for airway disease. Extent of risk varies by trade and work activity. Our data indicate the importance of bystander exposures and suggest that tunnel jacking may be associated with greater risk compared to more traditional methods of tunnel construction. A healthy worker effect is suggested.

Boston’s Jacked Tunnels Solve Interchange Challenge

The Central Artery in Boston, Massachusetts, known locally as the ‘Big Dig’, is a landmark project in urban infrastructure redevelopment. It was vital to minimise the disruption during construction. The tunnel jacking, which provided a key solution to this need, is by far the largest and most complex project of its kind in the world. Well over ten times the size of any jacked tunnels attempted in the USA before, it has involved a wide range of innovation. The tunnel jacking has delivered a low maintenance, robust construction while bringing important environmental benefits and contributed to over US$300 million in construction savings. The project has strongly demonstrated that, for particular spatial and operational constraints, tunnel jacking can provide the best overall value and performance in creating new infrastructure.

Boston's massive jacked tunnels set new benchmark

British tunnel-jacking expertise contributed to savings of over US$300 million on the vast project to build Boston's new subterranean highway network. The change from traditional cut-and-cover construction to tunnel jacking in frozen ground enabled three full-size interstate highway tunnels—totalling over 240 m in length—to be built in heavily obstructed ground under the approaches to a busy railway station with no disruption to service. The scale of the work was unprecedented, being several times larger than any tunnel-jacking project previously undertaken. It has set a new benchmark for the technique and further raised its profile as an effective and sustainable solution for creating new urban infrastructure.

Boston's massive jacked tunnels set new benchmark

British tunnel-jacking expertise contributed to savings of over US$300 million on the vast project to build Boston's new subterranean highway network. The change from traditional cut-and-cover construction to tunnel jacking in frozen ground enabled three full-size interstate highway tunnels—totalling over 240 m in length—to be built in heavily obstructed ground under the approaches to a busy railway station with no disruption to service. The scale of the work was unprecedented, being several times larger than any tunnel-jacking project previously undertaken. It has set a new benchmark for the technique and further raised its profile as an effective and sustainable solution for creating new urban infrastructure.

Performance of a single-propped wall during excavation and during freezing of the retained soil

Abstract A single-propped soldier-pile-tremie-concrete wall was constructed as part of the excavation support system for a tunnel jacking project. This wall supported a 14.3-m-high cut with a significant unbraced height (13.4 m) above the excavation subgrade. A limited area of the excavation subgrade next to the wall was jet grouted to provide stability against base heave. The jet grout also served as a “brace” for the wall below subgrade. The wall and prop were designed to support lateral loads during excavation as well as during ground freezing behind the wall. A ground freezing operation was implemented and carefully controlled to prevent wall yielding. Its success was facilitated by monitoring of wall movements, by drilling relief holes adjacent to the wall to reduce lateral heave pressures due to the soil freezing operation, and by limiting the exposure time of the wall to frost expansion. Measured wall behavior during excavation and during ground freezing is compared to those from finite element analysis for this very unique case history.

The analysis of deformations caused by loading applied to the walls of a circular tunnel

AbstractAn analytical solution to the problem of a load applied to a portion of the wall of a circular tunnel installed deep in a homogeneous isotropic material has been found. The solution is obtained by taking a Fourier transform, in the axial direction, of the field quantities and then representing these as a Fourier series in the polar angle. The integration which is necessary for the inversion of Fourier transforms has to be performed numerically using Gaussian quadrature.The solution has been used to analyse the problem of uniform normal loading applied over rectangular patches of the tunnel wall. An indication of how the solution can be applied to the tunnel jacking problem is given.

Ipswich sewer installed by tunnel jacking : Ground Engng, V16, N4, May 1983, P24–27

Ipswich sewer installed by tunnel jacking : Ground Engng, V16, N4, May 1983, P24–27

TBM + bentonite face up to 2km tunnel jacking job in IPSWICH : Tunn Tunnlg, V14, N4, May 1982, P54–55

TBM + bentonite face up to 2km tunnel jacking job in IPSWICH : Tunn Tunnlg, V14, N4, May 1982, P54–55

‘Earthworm’ system will threaten conventional tunnel jacking : Richardson, M; Scruby, J Tunn Tunnlg, V13, N3, April 1981, P29–32

Unitunnel is a method of inserting factory made pipe sections into the ground. Pneumatically inflated hoops interposed between the end of concrete pipe sections are used as toroidal flat jacks to propel the tunnel lining forward continuously as material is excavated at the face. The system overcomes many problems which have beset tunnel jacking in soft ground, particularly those of settlement and of high soil friction. (Author/TRRL)

Pipe jacking at the crossroads

Factors said to be preventing the development of pipe and tunnel jacking in the United Kingdom are described as lack of data available and lack of investment in underground works which prevents contractors from tooling-up. It is considered that a study should be financed by the TRRL and CIRIA to develop design and construction techniques, and to evaluate cost savings that can be achieved. Concrete pipe jacking is considered competitive with segmental tunnelling in the range 900-2550 mm diameter. Advantages of pipe-jacking are compared with cut-and-cover and auger boring tunnelling methods. (TRRL)

High load tunnel jacking test

High load tunnel jacking test